Add apt update to python linting

Author: mxmeinhold

.github/workflows/python-app.yml

@@ -19,7 +19,7 @@ jobs:
 
     steps:
       - name: Install ldap dependencies
-        run: sudo apt-get install libldap2-dev libsasl2-dev
+        run: sudo apt-get update && sudo apt-get install libldap2-dev libsasl2-dev
       - uses: actions/checkout@v2
       - name: Set up Python ${{ matrix.python-version }}
         uses: actions/setup-python@v2